The present invention relates generally to targets for light detection and ranging (“LIDAR”) systems. More particularly, this invention pertains to laser targets for laser guidance sensors used in rendezvous, docking and station keeping of mobile vehicles such as spacecraft. Even more particularly, this invention pertains to short range and long range laser targets used with advanced video guidance sensors (“AVGS”) employed in rendezvousing, docking and station keeping of mobile vehicles, such as spacecraft.
One AVGS known in the prior art enables a chase (active) vehicle and a target (passive) vehicle to rendezvous and dock with only the automatic piloting of the chase vehicle. When the AVGS operates in a ‘range and bearing’ mode, the AVGS on the chase vehicle searches for and illuminates two hemispherical long range laser targets attached to the target vehicle. The AVGS then detects the resulting reflected laser light and determines a range and bearing from the chase vehicle to the target vehicle.
When controlling docking or short range station keeping maneuvers, the AVGS shifts to tracking a separate three-point reflective docking target (short range docking target) mounted to the target vehicle. This short range docking target may be mounted away from the long range hemispherical laser target. A visual tracking sensor, such as a monochrome video camera, on the chase vehicle is used to detect the returns of the various laser targets and produce a video image of the detections. Software driven differential imaging techniques are used in determining the relative position and attitude of the vehicles.
Current reflector art used with the AVGS teach separate long range and short range arrays. Where this art is practiced on spacecraft such as the International Space Station (“ISS”), the need for multiple laser targets contributes to the potential confusion of laser targeting sensors such as the AVGS. The AVGS must ‘swap’ targeted arrays when handing off between long range and short range arrays. This requires searching for the short range sensor in an area of the processed detection image that is different than the area already identified as containing the reflections of the long range array. Also, additional hemispherical reflectors are needed for rangefinder style proximity sensors used for approaching and maneuvering around the ISS. These multiple reflectors arrays result in: additional sensor confusion; greater expenditures to design, build, transport and mount such arrays on the ISS; a greater number of astronaut extravehicular activities (“EVA” or ‘space walk’). For spacecraft not yet in orbit, this approach of using multiple reflectors arrays results in: more spacecraft surface area dedicated to the mounting the reflector arrays; greater spacecraft weight and greater spacecraft cost.
What is needed then, is a novel reflector assembly that can support rangefinders, AVGS long range tracking, and AVGS short range tracking from the beginning of a long range rendezvous approach through to final spacecraft docking.
Other features and advantages of the invention will be set forth in, or apparent from, the following detailed description of preferred embodiments of the invention.